import random

class Nucleotide:
    """Nucleotide"""
    
    def __init__(self, name, mass, charge):
        self.name = name
        self.mass = mass
        self.charge = charge

    def __repr__(self):
        return "Nucleotid %s mass:%d charge:%d " % (self.name, self.mass, self.charge)
        
    def __str__(self):
        return self.name
        
class NucleotideFactory:
    A = Nucleotide('a', 1, 0)
    T = Nucleotide('t', 1, 0)
    U = Nucleotide('u', 1, 0)
    
    nucleotides = [A, T, U]